A HILLER 1100 WAS DESTROYED BY FIRE AFTER A FORCED LANDING. THE PLT INDICATED THAT THE EGT HAD RISEN TO APPROXIMATELY 800 DEG C FROM 700 DEG AND THEN ROSE TO 1100 DEG. THE HEAT WARNING LIGHT ILLUMINATED. THE PLT INITIATED A PRECAUTIONARY LANDING. THE ENG FAILED IN THE DESCENT AND A AUTOROTATIVE LANDING WAS ACCOMPLISHED WITHOUT INCIDENT. THE ACFT WAS DESTROYED WHEN THE FIRE COULD NOT BE EXTINGUISHED. DURING THE ENG TEARDOWN, IT WAS OBSERVED THAT THE 1ST STAGE TURBINE WHEEL HAD EXTENSIVE BLADE TIP DAMAGE DUE TO EXCESSIVE TEMP. IT WAS NOTED ROTATING WHEELS AND STATIONARY NOZZLES WERE BADLY DAMAGED BY EITHER HEAT OR FOREIGN OBJECT DAMAGE (FOD) OR BOTH EXCEPT FOR THE #1 NOZZLE WHICH WAS IN GOOD CONDITION. THE VARIOUS COMPONENTS APPEARED TO HAVE BEEN ASSEMBLED PROPERLY EXCEPT FOR THE #6 ENG BEARING SEAL, WHICH WAS MISSING. IT COULD NOT BE DETERMINED IF THE ROPE TYPE SEAL WAS BURNT AWAY WITH THE EXCESSIVE TEMP OR IF IT WAS LEFT OUT OF THE ASSY.